/*
 * Copyright 2002-2016 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.springframework.web.reactive;

import reactor.core.publisher.Mono;

import org.springframework.web.server.ServerWebExchange;

/**
 * Interface to be implemented by objects that define a mapping between
 * requests and handler objects.
 *
 * @author Rossen Stoyanchev
 * @author Sebastien Deleuze
 * @since 5.0
 */
public interface HandlerMapping {

    /**
     * Name of the {@link ServerWebExchange#getAttributes() attribute} that
     * contains the mapped handler for the best matching pattern.
     */
    String BEST_MATCHING_HANDLER_ATTRIBUTE = HandlerMapping.class.getName() + ".bestMatchingHandler";

    /**
     * Name of the {@link ServerWebExchange#getAttributes() attribute} that
     * contains the best matching pattern within the handler mapping.
     */
    String BEST_MATCHING_PATTERN_ATTRIBUTE = HandlerMapping.class.getName() + ".bestMatchingPattern";

    /**
     * Name of the {@link ServerWebExchange#getAttributes() attribute} that
     * contains the path within the handler mapping, in case of a pattern match
     * such as {@code "/static/**"} or the full relevant URI otherwise.
     * <p>Note: This attribute is not required to be supported by all
     * HandlerMapping implementations. URL-based HandlerMappings will
     * typically support it but handlers should not necessarily expect
     * this request attribute to be present in all scenarios.
     */
    String PATH_WITHIN_HANDLER_MAPPING_ATTRIBUTE = HandlerMapping.class.getName() + ".pathWithinHandlerMapping";

    /**
     * Name of the {@link ServerWebExchange#getAttributes() attribute} that
     * contains the URI templates map mapping variable names to values.
     * <p>Note: This attribute is not required to be supported by all
     * HandlerMapping implementations. URL-based HandlerMappings will
     * typically support it, but handlers should not necessarily expect
     * this request attribute to be present in all scenarios.
     */
    String URI_TEMPLATE_VARIABLES_ATTRIBUTE = HandlerMapping.class.getName() + ".uriTemplateVariables";

    /**
     * Name of the {@link ServerWebExchange#getAttributes() attribute} that
     * contains a map with URI variable names and a corresponding MultiValueMap
     * of URI matrix variables for each.
     * <p>Note: This attribute is not required to be supported by all
     * HandlerMapping implementations and may also not be present depending on
     * whether the HandlerMapping is configured to keep matrix variable content
     * in the request URI.
     */
    String MATRIX_VARIABLES_ATTRIBUTE = HandlerMapping.class.getName() + ".matrixVariables";

    /**
     * Name of the {@link ServerWebExchange#getAttributes() attribute} containing
     * the set of producible MediaType's applicable to the mapped handler.
     * <p>Note: This attribute is not required to be supported by all
     * HandlerMapping implementations. Handlers should not necessarily expect
     * this request attribute to be present in all scenarios.
     */
    String PRODUCIBLE_MEDIA_TYPES_ATTRIBUTE = HandlerMapping.class.getName() + ".producibleMediaTypes";


    /**
     * Return a handler for this request.
     *
     * @param exchange current server exchange
     * @return a {@link Mono} that emits one value or none in case the request
     * cannot be resolved to a handler
     */
    Mono<Object> getHandler(ServerWebExchange exchange);

}
